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Denominators

Denominators. Demography in epidemiology FETP India. Competency to be gained from this lecture. Use demographic methods and data in applied epidemiology . Key elements . Demography Sources of information Demographic processes. Demography . Definition

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Denominators

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  1. Denominators Demography in epidemiologyFETP India

  2. Competency to be gained from this lecture Use demographic methods and data in applied epidemiology

  3. Key elements • Demography • Sources of information • Demographic processes

  4. Demography • Definition • Study of the size and distribution of human populations • Study of processes that bring about changes in these populations • Fertility and mortality (Biological) • Migrations • Objective • Study trends over time and variation across regions or subgroups in population processes Demography

  5. Factors affecting fertility and mortality • Proximate determinants • Ability to use contraception • Exogenous factors • Social, cultural, economic, psychological, environmental • Behavioural or life style factors • In some cases, access to or use of health services Demography

  6. Consequences of change in population processes: Example of ageing • Labour force and the economy • Child bearing in the adolescent and older ages • Women’s and children’s health and well-being • Population movements • Epidemiology of diseases Demography

  7. Sources of demographic data • Censuses • Vital registration systems • Sample surveys • Sample registration system (India) Source of data

  8. Sample registration system (SRS) in India • 1964-5 • Pilot basis • 1969-70 • Full scale • Dual reporting system • Provides estimates of birth and death rates at state and national levels • Regular publication of annual vital rates Demography

  9. SRS’ dual reporting system • Each event (birth or death) captured by two independent procedures • Continuous enumeration in population • Sample survey every 6 months • Events matched • Missing in both systems estimated • Evaluation of SRS • Under-enumeration does not exceed 5% Demography

  10. Sample design for SRS • Rural areas • Each district divided in two strata • Villages > 1500 population • Villages < 1500 population • Simple random sampling of villages and segments from the two strata without replacement • Urban areas • Sampling unit: Census enumeration block Demography

  11. Half yearly survey for SRS by full time supervisor from census directorate • Collects information on births and deaths from residents and visitors • Reference period: • Six month • 12 month to capture events missed during the last survey • Updates • House, household members and pregnant women list • Matching of events • Field verifications • Unmatched • Partially matched events Demography

  12. Sources of information on causes of death • Urban areas • Under SRS • Collection of information on medically certified deaths • Rural areas • Collection of data by paramedical staff using verbal autopsy techniques Demography

  13. Demographic processes • Number of people in an area at a given time: • Pt = Po + B - D +I -O • B= Births • D= Deaths • I= Immigrations • O= Out-migrations • From age structure to age composition Processes

  14. CDR Crude death rate ASDR Age specific death rate IMR Infant mortality rate NMR Neonatal mortality rate PNMR Post-neonatal mortality rate PMR Perinatal mortality rate Expectation of life at age x CSDR Cause-specific death rate MMR Maternal mortality rate Rates and ratios of mortality and pregnancy wastage Processes

  15. Age pyramid, India, 1961 and 2001 Influences risk of various illnesses and conditions as well as the health risk behaviours Processes

  16. Causes of death • Study the process of mortality • Stratified for • Still birth • Neonatal deaths • Infant deaths • Child deaths • Maternal deaths • Adult deaths Processes

  17. Determinants of mortality • Demographic factors • Age, sex, marital status and family size • Socio-economic variables • E.g., Income, education, religion • Health related behaviours • E.g., Smoking, alcohol and drug use • Disabilities and diseases • Type of death • Still birth, neonatal, infant, child, maternal and adult Processes

  18. Cause of death by verbal autopsy among > 5 years of age, Tamil Nadu, India, 2004(ICD 10) Processes

  19. Life tables • Study longevity, success rates and hazards • Ordinary life tables • Studies attrition from a cohort resulting from a single factor • Multiple decrement life tables • Attrition due to more than one factor • Multi-state life tables • Move through different states Processes

  20. Cause elimination using life tables • Objective • To eliminate the effects of competing risks of dying from various causes on the risk of dying from a given cause • To measure the ‘pure’ severity of the cause • Example • To study the mortality of HBV infection acquired at birth, one has to subtract, year by year, the mortality from other causes since there is a long delay between infection (at birth) and death (during adulthood) • Method • Construct life table in which all causes are eliminated except one particular cause Processes

  21. Population distribution: Size and density of the population by geographic subdivision • GIS (Geographic information system) • Organized collection of computer hardware, software, geographic data and personnel designed to efficiently capture, store, update, manipulate, analyze and display all forms of geographically referenced information • Useful to study trends and spatial pattern of population processes • Provide insights into the location and distribution of public health needs and resources Processes

  22. Fecundity and fertility • Frequency of live births in a population • Fecundity • Ability to produce live offspring • Cannot be measured • Can be assessed clinically • Fertility • Actual production of live offspring Processes

  23. CBR Crude birth rate GFR General fertility rate ASFR Age-specific fertility rate TFR Total fertility rate GRR Gross reproduction rate NRR Not reproductive rate PPR Parity progression ratio MBI Mean birth Interval Measures of fertility Processes

  24. Determinants of fertility • Focus on proximate determinants • Include • Exposure to sexual intercourse • Exposure to conception • Gestation and successful parturition Processes

  25. Contraception • Conventional • Permanent • Abortion to unwanted pregnancies • Failure Processes

  26. Adolescent pregnancies • May cause sexually related problems including sexually transmitted diseases • Induced abortion • Improper child development • High mortality risk for mother and babies Processes

  27. Migration • Definition • Movement of people from usual (primary) residence to another • Involves crossing an administrative or political boundary • Most difficult to measure Processes

  28. Nuptiality: Marriage and marital dissolution • Frequency of marriages • Characteristics of persons joining • Dissolution • Separation • Divorce • Death • Crude marriage rate • Age and sex specific marriage rate • General marriage rate • Median or mean age at marriage Processes

  29. Estimations and projections on the basis of census data • Inter-censal • Post-censal • Future (Projection) Processes

  30. Take home messages • Demography is closely related to epidemiology • Sources of information are diverse and cross validate each other • Demographic processes are studied by time, place and person

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